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I had a discussion about this with my coworker. It appears that global warming (even up to +6K) has advantages:

  1. increased plant growth: increase in photosynthesis efficiency
  2. more water evaporation from oceans which will cause more rains even in dry places like Africa
  3. Warmer winters that will allow humans to grow more food. Greenland will become green again

Only drawbacks I could find were:

  1. More power consumption in summer for AC, compensated by less power consumption in winter for warming
  2. Intense evaporation and temperature difference will cause strong winds and storms, but it will cause more rain in distant places which is better. Building advanced city drain systems like in Japan can mitigate this problem for cities
  3. Coast line change due to water level rise. Modern engineering allows the building of islands, and that technology will probably improve with technological progress
  4. Increase in power losses in electrical lines. For copper it's only 0.393%/K, also can be mitigated with usage of advanced modern insulators that enable higher voltages for energy transfer

The drawbacks look small to me, and I also describe how they can be compensated. Are there any more?

So why is global warming bad?

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    $\begingroup$ Largest problem is that some places which today hold a lot of populace is likely to become inhospitable. The suffering, migration and certainly, the wars and the lawlessness makes it a very very very bad trade. $\endgroup$
    – Stian
    Jun 18, 2023 at 14:22
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    $\begingroup$ @Itération122442: Of course humans are part of nature. But when I mess up my own living room I don’t say “oh, nature messed up my living room”. $\endgroup$
    – Michael
    Jun 19, 2023 at 7:14
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    $\begingroup$ Your list of drawbacks does not include extreme weather conditions. One would be well-advised to not underestimate the word "extreme" in this context. These conditions may, by some estimates, cause 1.2 billion refugees by 2100. Good luck handling such numbers peacefully. The number of refugees in all of human history has been estimated at a little less than 1/10th of that, and you're probably well-aware of the effects of that even just in your own lifetime. $\endgroup$
    – Sixtyfive
    Jun 19, 2023 at 15:07
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    $\begingroup$ @Sixtyfive an increase of 6 kelvin is the same as an increase of 6 celcius. Those scales have the same unit size, they just start from a different place. $\endgroup$
    – njzk2
    Jun 19, 2023 at 20:50
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    $\begingroup$ I think this question is an attempt to debate and is not sincere. The points included are simplistic and misleading repetitions of popular objections to science based expert advice, to expert assessments of the likelihoods of environmental and economic harms (including vs benefits) and objections to actions to address human caused climate change. Vote to close. $\endgroup$
    – Ken Fabian
    Jun 19, 2023 at 22:51

10 Answers 10

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Global warming is colloquially referred to as the human-made warming of the climate that would not have otherwise occurred without the industrial revolution. The greenhouse effect, which is the mechanism that leads to warming, is in fact necessary for life on earth since the temperature of Earth would be too cold without it. The amount of carbon in the atmosphere has fluctuated greatly over millions of years, naturally, but we are greatly affecting it now. From Global Warming 101, the detrimental effects of a rapidly warming Earth are:

  • more frequent extreme weather events
  • disappearing glaciers, early snowmelt, and severe droughts will cause more dramatic water shortages and increase the risk of wildfires
  • rising sea levels will lead to even more coastal flooding
  • forests, farms, and cities will face troublesome new pests, heat waves, heavy downpours, and increased flooding. All of these can damage or destroy agriculture and fisheries.
  • disruption of habitats such as coral reefs and alpine meadows could drive many plant and animal species to extinction.
  • allergies, asthma, and infectious disease outbreaks will become more common due to increased growth of pollen and the spread of conditions favorable to pathogens and mosquitoes.

If we take a look at your list, we should make some revisions to the advantages:

increased plant grow (increase in photosynthesis efficiency)

Increases in CO2 don't benefit photosynthesis in hotter/drier conditions. Plant stress due to water availability and extreme heat are more influential than increases in CO2.

more water evaporation from oceans that will cause more rains even in dry places like Africa

That sounds nice, but actually the increased water moisture and heat in the atmosphere lead to more extreme weather events and can shift seasonal weather patterns under different climate conditions. This means more floods and tornadoes and hurricanes, etc. That water doesn't infiltrate into the soil like seasonal rain does.

Warmer winters that will allow grow more food (Greenland will become green again)

The loss of ice from glaciers leads to sea-level rise and loss of coastland cities due to flooding events. Not sure if they will want to move to Greenland.

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    $\begingroup$ I'd add that the detrimental affects to humans are in reasonable part due to the speed of change. If the same level of warming happened over (say) a few hundred years, we'd happily adapt (perhaps by moving away from hotter/drier areas, spending time to cultivate newly available land, etc) - as has presumably happened in the past. However, this change is currently happening in (say) 50 years, which means (potential) mass migrations, mass famines, mass flooding, etc - which we're far less well equipped to cope with. $\endgroup$ Jun 18, 2023 at 19:47
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    $\begingroup$ I would have posted this as an answer, but I don't have any data to back my claim: "disruption of habitats" is an important factor in my opinion. It may be relatively trivial for some of us to adapt to the new environments with the help of technology. However, the world is not comprised of just human-beings. And when the natural equilibrium in which some creatures have been used to living is disrupted so abruptly, they may not be able to adapt fast enough. And when you start removing stuffs at the bottom of the food chain... well, there ain't going to be anything left in the end. $\endgroup$
    – Clockwork
    Jun 18, 2023 at 19:50
  • $\begingroup$ Greenland is quite high. I played with a flood map tool online, even with 100 or 400m of ocean level elevations, I didn't see as drastic change in the coastline as with the other nations. Of course most of the settlements are on the coast next to the ocean. $\endgroup$ Jun 19, 2023 at 18:31
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    $\begingroup$ "Global warming is colloquially referred to as the man-made warming of climate that would not have otherwise occurred without the industrial revolution" I think you have that backwards. Anthropogenic warming of climate is colloquially referred to as "global warming". $\endgroup$ Jun 19, 2023 at 23:41
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    $\begingroup$ increased evaporation also makes dry places even drier, it does not make everywhere wetter, mostly wet places get wetter and dry places get drier. $\endgroup$
    – John
    Jun 20, 2023 at 21:36
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Our current economy is a rather fragile thing. Even a small war in central Europe has caused supply chain issues and painful inflation around the whole world. Any kind of major disruption would be disastrous, where by disastrous I mean cause major reductions in the standard of living for a large part of the world's population.

Eight of the top 10 largest cities in the world - Tokyo, Mumbai, New York City, Shanghai, Lagos, Los Angeles, Calcutta and Buenos Aires - are on or near the coast. At best uncontrolled climate change would require massive spending to create flood defences, and at worst it would render large parts of these cities uninhabitable and displace hundreds of millions of people. I think you would agree this counts as major disruption.

The problem is not that we could not construct a modern civilisation in a warmer world. As you point out, the issues caused by higher temperatures are not necessarily problems. If our society had developed from hunter gathers in a warmer climate we'd simple have built our cities farther inland. The problem is how we transition from our current state to a warmer world. We cannot just pick up New York and move it a few miles inland

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    $\begingroup$ One single ship caused multiple months of disruption due to knock-on effects, despite only being stuck in Suez Canal for only ~6 days. Our world economy is a house of cards. $\endgroup$
    – Criggie
    Jun 19, 2023 at 4:34
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    $\begingroup$ @Criggie which climate change could easily knock down! $\endgroup$ Jun 19, 2023 at 5:31
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    $\begingroup$ "small war on central Europe" - [citation needed]. I know what war is being referenced here. My issue is with the characterization. $\endgroup$ Jun 19, 2023 at 18:32
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    $\begingroup$ @MindwinRememberMonica About 50% of the Iraq War in terms of personnel, about 15% of the Vietnam War, or <1% of WWII can be considered small in a historical context. $\endgroup$
    – Therac
    Jun 19, 2023 at 19:07
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    $\begingroup$ @Therac that's highly subjective. And off-topic. We can consider both of our comments perfectly valid opposing opinions and move on. You can even consider my refusal to further elaborate as a win. I don't mind. $\endgroup$ Jun 20, 2023 at 11:34
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This is a question with a very wide scope and complex answers with much uncertainty. However, I have found Carbon Brief's interactive explainer a good starting point. This, however, has limited coverage of issues beyond 2C because it relies on published papers.

If I understand you correctly, a rise of 6C over preindustrial levels would almost certainly have drastic consequences for humanity. That would almost certainly push the wet-bulb temperature in the tropics over 35C, making large areas of the Earth's surface uninhabitable for all or part of the year.

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    $\begingroup$ Web-bulb temp, particular for overnight lows, is a great indicator for whether the weather will simply kill people who can't escape it. $\endgroup$
    – X Goodrich
    Jun 19, 2023 at 14:44
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Have you ever been at 47 degrees Celsius (118 F) outdoors? I have, and it is unbearable. Right now Arizona is at 41 C (106 F), 6 more degrees means 47 C. Plus those places already at 47 C will go to 53 C (127 F), making them worse than the Sahara desert. This is just the average; it will likely be worse in some places.

Most people in the tropics will die or be forced to migrate. We are not speaking about your ordinary migratory pressure: making large areas of the globe inhospitable means that hundreds of millions of people will be displaced forcefully from their communities. Since there is not a lot of empty space on the globe, this will cause huge pressure on the rest of the world.

Mind you, 1/3 of people live in the tropics, where temperatures of 45+ C are not uncommon. Most of the population cannot afford air conditioning even now, and the cost of cooling a house at 53 C would probably be thousands of dollars per month in the best possible scenario. In countries where average income per capita is a few thousand dollars per year this is out of the question. Supposing the electric grid could stand it. That is without ever leaving your house.

So it looks pretty bad to me, even without taking into account the hurricanes, the extreme droughts, the sea raises, the loss of natural habitats and all the other nasty predicted effects from climate change. Sure, a few areas like Greenland may become nice and warm, but it is not enough to offset all the bad things.

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    $\begingroup$ A much bigger problem than human survivability in warm weather is water supply and plants. Even if we’d be fine in 60°C weather, what are people in those regions going to drink and eat? $\endgroup$
    – Michael
    Jun 19, 2023 at 7:11
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    $\begingroup$ Much bigger? I would assume what to eat and drink is also part of the survivability issue. $\endgroup$ Jun 19, 2023 at 7:42
  • $\begingroup$ Yes, but you make it sound as if it could be mitigated with a bit of A/C. $\endgroup$
    – Michael
    Jun 19, 2023 at 8:48
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    $\begingroup$ It's worse than that, because the average temp will go up by 6C, which means that some areas will see significantly more rise than that. $\endgroup$ Jun 19, 2023 at 10:00
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    $\begingroup$ @alexfernandez A/C at 35°C only costs hundreds of euros per month in houses that are built poorly. With night cycling, good insulation, and other measures to protect against unwanted heat, it costs a fraction of that. It is in any case urgently needed to massively upgrade the insulation of houses that are heated or cooled. $\endgroup$
    – gerrit
    Jun 19, 2023 at 11:31
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Apart from sea level rise which will force billions to relocate, rising temperatures which will render large parts of the Earth uninhabitable by humans, a major problem is extreme weather.

If you shift a normal distribution, extreme values on the high end become much more frequent.

extreme values
Source

(Note that due to changing dynamics, in some regions, cold extremes can become more frequent — it's complicated)

This is why, due to climate change, we are already seeing unprecedented droughts and fires and unprecedented floods. Just in the past five years, extreme weather caused 100 billion dollar in insured losses — that does not include uninsured losses. Most of the world population are not insured against losses, and some extreme weather will become so frequent in some regions it becomes uninsurable. A single hailstorm can cause more than 1 billion dollar in damage.

Apart from contributing to mass extinction and immense human suffering, climate change is expensive. Humans are extremely sedentary creatures, building dwellings lasting 3-15 generations or more and cities lasting 100+ generations. Human civilisation thrived during the holocene, which had a remarkably stable climate. We've messed that one up and entered the anthropocene, throwing away the best thing the planet has ever given us. Could we survive in a warmer climate with more extreme weather? As a species, probably. It would be immensely expensive, and generations after us will curse us for making life in the next 50-1000 years much harder and more expensive than it might have been if we had acted sensibly.

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  • $\begingroup$ The temperature would increase on average, but there would also be more extreme cold events because of disruptions to global weather patterns and whatnot. From this graphic, one might conclude that an abnormally cold winter would be evidence against climate change (a common sentiment), but this is part of what climate change predicts. $\endgroup$
    – NotThatGuy
    Jun 20, 2023 at 14:34
  • $\begingroup$ @NotThatGuy In some regions, yes. On average, no. I didn't want to make it too complicated, but you're right about the "evidence against climate change" point — I've added a note to the answer. $\endgroup$
    – gerrit
    Jun 20, 2023 at 14:49
  • $\begingroup$ @gansub I don't think so. $\endgroup$
    – gerrit
    Jun 21, 2023 at 6:49
  • $\begingroup$ @gansub Single tailed tests are for single tailed distributions AFAIK, and anyway, we're not doing a test at all here, just describing how the frequency of extreme events (or events that were previously considered extreme) can become much more likely even if the mean shifts only moderately. $\endgroup$
    – gerrit
    Jun 21, 2023 at 10:02
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Water Shortages

By now, the melting/retreat of glaciers is perhaps the most well-established proof of warming temperatures regardless of what you believe about weather satellites and the greenhouse effect. While glaciers don't directly provide much fresh water, they are a direct proof of average snowfall and winter temps. Shrinking glaciers obviously mean less snowfall, which means less meltwater, which means less freshwater feeding streams and rivers.

A lot of agriculture depends not just on rain, but on these water sources, and reduced water availability is felt keenly, such as this case in Alberta, CA. It's not just crops on farms that are suffering. Cattle depend widely on natural forage, so when there isn't enough water for wild grasses and shrubs, it affects the entire food chain/ecosystem.

This isn't just one or two farms having trouble, either. The entire province declared a state of emergency due to the extremely dry conditions. If there are other farmers who are benefiting from better weather, they sure aren't crowing about it in the news cycle. Nor are investors shilling their shares to trump up demand. There is certainly no talk of a Greenland farming boom.

Wildfires

Fires need fuel. Trees work very hard to pull water out of the ground, transpiring it into the air as part of photosynthesis. This also has the secondary effect of lowering the average temperature around them (as anyone who has walked by a tree on a hot day can tell you vs. standing under a manmade shade). Healthy trees with a good water supply thus make for bad firewood and are very resistant to wildfires. On the other hand, hotter weather often means less rainfall, and more importantly, dehydration of all plants, as the higher temperatures increase the water capacity of the atmosphere and thus reduce the relative humidity. For dead plant matter normally undergoing natural composting, this means instead of being food for bacteria and fungi, it becomes food for wildfires.

NOAA assesses that climate change has been the primary driver of increased fires in the recent record years. It's quite amusing that you call greater evaporation a good, when it's quite obvious that it's a serious bad.

Thawing Permafrost

You mention higher winter temps as a positive effect, which totally ignores the fact that both humans and nature depend on cold winter temperatures. Normally, the fossil fuel industry would support the "warming isn't bad" argument, but anyone who lives in Alaska can tell you that the oil industry relies heavily on permafrost for arctic drilling. The year-round ice makes for a reliable and sturdy surface for roads and buildings. When it melts the oil industry is negatively impacted. On top of that, organic matter that was frozen for possibly thousands of years now releases methane into the atmosphere as the permafrost melts, further accelerating climate change.

Decreased Nutrition

While elevated CO2 will indeed cause plants to grow larger, on average, what it mainly does is increase the carbohydrate content and cause larger leaves. What it doesn't do is increase the nutritional content of the plants. So carb-heavy crops like wheat get a net gain, but most other crops become less nutritious because they are bigger, but with the same amount of nutrients (like protein and vitamins). That's because nutrient production is usually limited by soil composition, and higher CO2 doesn't magically cause increased nitrogen or trace minerals in the soil. You might have to eat 20% more watermelon or orange to the get same nutrients you do today, which is wasted metabolic energy for digestion. Not a win.

As far as increased wheat productivity, with the rise of gluten sensitivity, I hardly think that increasing our carb production is the pathway to a healthier society. We are already overflowing with carbs, and an excess of carbs could easily be described as the primary driver of obesity.

Conclusion

Literally all of your "pros" are actually "cons" when you take a closer look. We don't have to wait 50 years to tell whether climate change is going to be a net positive or not. We can see it in action today. And the only beneficiaries of it that I have seen so far are mining interests that want to explore the Arctic (Russia in particular) now that there are so many more ice-free days (and perhaps it will become permanently ice-free).

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    $\begingroup$ A permanently ice-free Arctic is not foreseen, but an ice-free Arctic every summer is possible. For the Arctic, not only mining but also the shipping industry benefits. The mild winter has helped Central Europe in times of gas shortages and high energy prices. But certainly, the overall long-term effect is overwhelmingly negative. $\endgroup$
    – gerrit
    Jun 20, 2023 at 10:36
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Regarding your first point: "increased CO2 causes increase in photosynthesis efficiency". While this is true, there is a caveat:

Plants do indeed grow faster, but at the expense of decreased protein and micronutrients (see e.g. here). So while one may get more of C3 crops (rice, wheat, ...) they are then of lower quality, at least regarding protein content ("carbon dilution effect"). So one partly loses what was gained. There seems to be a direct causal link, because C4 plants which do not benefit from elevated CO2 leaves do not show the carbon dilution effect (see Introduction here))

Perhaps for some plants this effect is not strong, or can be mitigated with special treatment. I am not sure if everything is already well understood and if solutions to the problems can be found, if the problems are so bad that they need mitigation. But perhaps it is not valid to label increased CO2 an advantage per se (a betterdscription would probably be "potential advantage" or just not list it as advantage).

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In short, because it is happening quicker than any possible "adaptation" of life to it, putting a lot of biological stress on the environment.

For the humans, it is bad because our infrastrucutre is hyper-specialized and very fragile.

Much of our human infrastructure has been built with the water table and the sea level being at a certain level, as well as much of the agricultural infrastructure is dependent and optimized for narrow temperature and humidity ranges at predefined latitudes.

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Don't forget ocean acidification, increased CO2 leads ot acidification of the ocean, which kills coral and other photosynthetic life, so you get a net LOSS of photosynthesis.

Also it does not necessarily lead to much increase in photosynthesis on land. 1 extreme heat often reduces photosynthetic efficiency and 2 few plants are limited by CO2, limitation by nitrogen is more common so increased CO2 does not get you more photosynthesis.

https://pubmed.ncbi.nlm.nih.gov/15143433/

https://www.nature.com/articles/s41598-019-40620-8

https://www.frontiersin.org/articles/10.3389/fmars.2019.00322/full

https://news.climate.columbia.edu/2022/01/27/how-climate-change-will-affect-plants/

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We refer to it as "Climate Change" now rather than "Global Warming" to reflect how places will get extremely hot and/or extremely cold sometimes sporadically with little warning. The balance and the whole ecosystem of how our world operates has been upset.

For instance in the UK we had "Beast of the East" (https://inews.co.uk/news/when-was-the-beast-from-the-east-what-happened-in-2018-and-if-similar-uk-weather-is-coming-2186341) that caused disruption due to extremely cold weather.. sometimes -10oC... then a record heat wave later.

Climate Change does not cause all bad weather of course.. but it can make bad weather 20 times more likely : https://www.theguardian.com/environment/2022/oct/05/climate-crisis-made-summer-drought-20-times-more-likely-scientists-find

This flip flop of extreme cold and extreme heat makes it very difficult for people to heat and cool (for instance in the UK we do not predominantly have airconditioning in our homes) and can lead to incredibly expensive gas bills in winter.

People's homes are being flooded that were never previously likely to be flooded and in other places people's homes are going up in flames with fires that would never have been imagined before.

Then there's all the species of animals and plants that are being wiped out because it's too hot. Corals are bleaching and then dying in the seas.. https://www.earthday.org/how-climate-change-is-threatening-our-species/ You might not specifically care about bees etc, but if you are relying on them to pollinate plants that ultimately end up as being your food this all puts everything into chaos.

The death of plants, people and animals is more than an inconvenience and scientists refer to certain "tipping points" (examples at https://www.theguardian.com/environment/2022/sep/08/world-on-brink-five-climate-tipping-points-study-finds) that trigger at different thresholds of climate change... i.e. A certain amount of the ice caps melting is predicted to raise the sea level to a certain level that entire countries will be under water.

  • 71% of the 504 extreme weather events and trends included in the map were found to be made more likely or more severe by human-caused climate change.
  • 9% of events or trends were made less likely or less severe by climate change, meaning 80% of all events experienced some human impact. The remaining 20% of events and trends showed no discernible human influence or were inconclusive.
  • Of the 152 extreme heat events that have been assessed by scientists, 93% found that climate change made the event or trend more likely or more severe.
  • For the 126 rainfall or flooding events studied, 56% found human activity had made the event more likely or more severe. For the 81 drought events studied, it’s 68%.

Source: https://www.carbonbrief.org/mapped-how-climate-change-affects-extreme-weather-around-the-world/

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